Percentage Calculator
Percentages come up in three common flavors — this calculator handles all three: finding what a percentage of a number is, finding what percent one number is of another, and finding the percent increase or decrease between two numbers.
How the Percentage formula works
The three core percentage formulas:
X% of Y = (X / 100) × Y X is what % of Y = (X / Y) × 100 Percent change = ((New − Old) / Old) × 100
Step-by-step calculation
- Choose which of the three percentage problems you're solving.
- Enter the two known values into the corresponding fields.
- The calculator applies the matching formula automatically.
- Read the result, rounded to two decimal places.
Worked example
What percent increase is it from 80 to 100? Percent change = ((100 − 80) / 80) × 100 = (20 / 80) × 100 = 25%.
Frequently asked questions
How do I calculate a percentage decrease?
Use the same percent-change formula: ((New − Old) / Old) × 100. If the new value is smaller than the old value, the result will be negative, indicating a decrease.
What's the difference between 'percent of' and 'percent change'?
'Percent of' finds a portion of a single number (like 20% of 50). 'Percent change' compares two different numbers to find how much one differs from the other, as a percentage.
Can percentages be over 100%?
Yes — if a new value is more than double the old value, the percent increase will exceed 100%. Percentages simply express a ratio scaled by 100, with no inherent upper bound.